The invention relates to under-surface drain systems and particularly systems for bunkers in golf courses, drainage areas in sports fields, such as the areas along the sides of tennis courts, and football, baseball, and soccer fields; and landscape areas where under-surface drainage systems are required or preferred for consistent surface appearance and integrity.
A golf course imposes unique design requirements on turf systems and sand bunkers on the course. Bunkers are deliberately positioned to create artificial hazards for errant golf balls The bunkers are typically constructed as depressions having a clay base with sloped sidewalls rising upward to surrounding turf. The bunkers have specific peripheral configurations, depth, and sloped sides. Sand overlays the clay base or other base material to provide the playing surface for golf balls. The sand is typically groomed daily by hand or with motorized equipment to present an even surface to the golfers. Rakes and other equipment fluff the top surface of the sand to present the desired surface. A drainage system for bunkers should be located below the surface of the sand a sufficient distance to allow regular sand shots to be taken above the drainage system.
In wet climates, rainwater compacts the sand and mixes the sand with the underlying clay base. Clay particles or “fines” discolor the overlying sand and also alter the playing qualities of the bunker. Various efforts have been made to reduce the commingling of sand and clay particles and to prevent other contamination of the sand. As shown in U.S. Pat. No. 5,746,546 to Hubbs et al. (1998), fiber strands and water absorbent particles such as psyllium may be added to soil to improve the soil shear strength.
Other bunker systems use geotextile fabrics underlying the sand. Fabric liners do not easily retain the sand on the sloped sides and are subject to rupture and other failure. Such liners do not independently correct the problems associated with accumulation of rainwater in the bunkers.
Because the bunkers comprise depressions in the soil, rainwater collects in the bunkers and must be drained to another location. Perforated pipe has been installed in the bottom of bunkers to drain excess water to a water discharge line. Gravel has been packed around the exterior surface of the perforated drain pipe to form a French drain. Such systems eventually fail in wet climates because the clay linings are susceptible to erosion. Clay particles and other contaminants such as grass clippings pack around the perforated pipe to lower the fluid transmissivity of the gravel, and such particles further enter the pipe interior. Over time the accumulated intrusion clogs the pipe which requires new construction of the entire bunker. Such construction is not only expensive to accomplish but also disrupts the utility of the golf course during construction.
Landscape areas whether mulched; sand and stone; grass of various types; and flowerbeds should have unique under-surface design to preclude standing water in low areas. Standing water in low areas contributes to damage of living plants in landscaped areas and leaves residual flotsam, debris and watermarks which destroy and compromise the surface design and appearance.
Drain systems have been developed for other applications such as large playing fields. For example, U.S. Pat. No. 5,648,856 to Bohnhoff (1998) discloses a thermoplastic mat underlying the surface which facilitates capture of water within an inflatable container for redistribution to the turf surface. Bohnhoff further describes conventional perforated pipe networks and the problems associated with poor drainage. Large playing fields usually require drainage along the sides of the fields. The fields are usually rounded to drain toward the sides. These fields need a drainage system which is below the playing surface to avoid interference with the play of the game and support activities around the fields.
In bunkers having perforated pipe drains, clay fines inevitably pack off the pipe at the lowest point in the bunker. This occurrence causes excess water to pond at this position within the bunker, further accelerating deterioration of the bunker drainage system. A need exists for an improved bunker drainage system which facilitates water drainage from bunkers and facilitates maintenance operations, and for a water drainage system for other sports fields which can be located below the sports surface to avoid interference with play and field use above the drainage system.